Polyunsaturated fatty acids (PUFAs), including omega-3, omega-6 and omega-9 fatty acids, are vital to everyday life and function. For example, the beneficial effects of omega-3 fatty acids like all-cis-5,8,11,14,17-eicosapentaenoic acid (EPA) and all-cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) on lowering serum triglycerides, preventing cardiac arrhythmias, stabilizing atherosclerotic plaques, reducing platelet aggregation, and reducing blood pressure are well established. See e.g., Dyrberg et al., In: Omega-3 Fatty Acids: Prevention and Treatment of Vascular Disease. Kristensen et al., eds., Bi & Gi Publ., Verona-Springer-Verlag, London, pp. 217-26, 1995; O'Keefe and Harris, Am J Cardiology 2000, 85:1239-41; Radack et al., “The effects of low doses of omega-3 fatty acid supplementation on blood pressure in hypertensive subjects: a randomized controlled trial.” Arch Intern Med 151:1173-80, 1991; Harris, “Extending the cardiovascular benefits of omega-3 fatty acids.” Curr Atheroscler Rep 7:375-80, 2005; Holub, “Clinical nutrition: 4 omega-3 fatty acids in cardiovascular care,” CMAJ 166(5):608-15, 2002. Other benefits of PUFAs are those related to the prevention and/or treatment of inflammation and neurodegenerative diseases, and to improved cognitive development. See e.g., Sugano and Michihiro, “Balanced intake of polyunsaturated fatty acids for health benefits.” J Oleo Sci 50(5):305-11, 2001.
Sources of beneficial PUFAs include diets rich in PUFAs, nutritional supplementation, or pharmaceutical compositions. These sources typically contain or are derived from marine oils such as fish, but PUFAs can also be derived from microbial sources including various species of Thraustochytrids. Plants are also natural sources of PUFAs and have even been modified genetically to include genes that produce various PUFAs in further efforts to reduce costs associated with commercial production of PUFAs.
Oils containing PUFAs usually require at least some level of purification and processing to concentrate the beneficial PUFAs and to remove unwanted components. Processes for purifying or concentrating PUFAs are usually multistep processes that vary depending on the particular product desired. One step that is sometimes performed is known as urea complexation. Urea is known to form complexes with organic compounds having long, straight carbon chains, such as saturated and monounsaturated fatty acids or esters. (See Marschner, “The Story of Urea Complexes,” Chem & Eng News, 33(6):494-6, 1955; Hayes et al., “Urea Complexation for the Rapid, Ecologically Responsible Fractionation of Fatty Acids from Seed Oil, JAOCS 75(10):1403-1409, 1998). Urea forms a complex when combined with the saturated and monounsaturated fatty acids/esters components of the oil, forming what is sometimes called a urea adduct or clathrate. Then, the adduct, including its saturated and monounsaturated fatty acids/esters, is separated from the oil, generally by filtration.
The result of urea complexation is oil with a higher concentration of PUFAs and reduced saturated or monounsaturated fatty acid/ester content. In most processes, the urea adduct is discarded, which is wasteful and inefficient, especially when the adduct can also contain PUFAs in significant amounts. Other processes, such as those disclosed in Hayes et al., focus on recovering residual PUFAs from the adduct and discard the urea.
In light of the health benefits of PUFAs such as omega-3 and omega-6 fatty acids, and the deficiencies with existing methods of urea complexation, it is desirable to find new and cost-effective ways to separate PUFAs from a urea adduct and ways to recycle the urea. The methods disclosed herein address these and other needs.